This invention relates to a light-sensitive silver halide photographic material having high sensitivity and also excellent in sharpness of images, and an image-forming method and a photographing method of the same.
In general, films for X-ray photography utilized in medical diagnoses are employed in combination with X-ray fluorescent intensifying screens at the time of photographing. This is because in consideration of influence of X-rays to human bodies, X-rays which have been transmitted through a front X-ray fluorescent intensifying screen are to be further utilized in a rear X-ray fluorescent intensifying screen for the purpose of utilizing X-rays effectively.
In recent years, sensitivities of films and X-ray fluorescent intensifying screens have become higher, and also a higher quality of images for medical diagnoses has been demanded increasingly. Particularly, for observing conditions of focuses or diseased parts more precisely, improvement in sharpness has been strongly demanded.
However, in a light-sensitive silver halide photographic material for X-rays having an emulsion coated on both surfaces, a light irradiated from one X-ray fluorescent intensifying screen is transmitted through an adjacent silver halide emulsion layer, and the light is scattered by a support to cause from both surfaces a so-called crossover exposure phenomenon that a silver halide emulsion layer on the other side is subjected to imagewise exposure, which becomes a great factor to deteriorate sharpness of images.
For reducing a crossover exposure from both surfaces and improving sharpness, there have been made many proposals as disclosed in Japanese Unexamined Patent Publication No. 132945/1986 or U.K. Patent No. 821,352 in which a dye is used in a silver halide emulsion layer or a constituent layer.
Further, improvement has been made not only in films but also in X-ray fluorescent intensifying screens, and, for example, Japanese Unexamined Patent Publication No. 110538/1990 discloses a technique in which silver halide emulsion layers having different color sensitivities are provided on an A surface and a B surface, and X-ray fluorescent intensifying screens having emission spectra corresponding to the respective color sensitivities are used.
However, even in these improved techniques, as long as two sheets of X-ray fluorescent intensifying screens are used on both surface emulsions, deterioration of sharpness cannot be avoided, and particularly, in X-ray photography system, oblique photography in which X-rays are incident obliquely relative to a film surface cause slippage of images of both surfaces, which results in significant deterioration of sharpness.
Also, for improving sharpness, there has been made an attempt that an emulsion layer is provided only on one surface and exposure is effected only from one side. However, there are inconveniences that a sensitivity is low, and that when a sensitivity at one side is to be made higher, a film thickness of a light-sensitive emulsion layer will be increased as a matter of course, and fixing property, washing property or drying rate at one side is lowered, whereby color leftover and deterioration of images due to residual silver and residual hypo are brought about undesirably.
The present inventors have investigated variously a method for improving sharpness of a light-sensitive silver halide photographic material having a silver halide emulsion layer on both surfaces by making sensitivities and amounts of silver coated different between an emulsion layer at one side (A surface) and an emulsion layer at the other side (B surface) and using a X-ray fluorescent intensifying screen only at one surface, and consequently found that since the (A) surface and the (B) surface are composed of different emulsions, amounts of silver and amounts of a binder, respectively, surface physical properties of the (A) and (B) surfaces of a film are not balanced.
For example, when the (A) surface and the (B) surface have different amounts of a binder mainly composed of gelatin and amounts of silver, respectively, tensile strengths of film surfaces become different, whereby undesirable phenomena that a film is curled, and that when control of water contents of the both surfaces is insufficient, films are adhered to each other are observed.
In recent years, photographing systems of X-ray films have been automated, and automatic film conveying property has become one of the most important performances. Under this situation, since curling and adhesion of the film are serious defects, improvement has been demanded urgently
Further, it is extremely difficult to distinguish between a front surface and a rear surface of a film having an emulsion layer on both surfaces and to handle it in darkrooms, and generally, there is a great possibility of mistakes.
This is one reason why a film having a front surface and a rear surface with different characteristics has not been employed so far. Therefore, it is required urgently to accomplish a system in which photography can be conducted without using a front surface and a rear surface reversely by mistake when a film having a front surface and a rear surface with different characteristics is used.